WO2016134469A1 - Apparatus for measurement of optical transmission using fluorescence radiation - Google Patents

Apparatus for measurement of optical transmission using fluorescence radiation Download PDF

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Publication number
WO2016134469A1
WO2016134469A1 PCT/CA2016/050186 CA2016050186W WO2016134469A1 WO 2016134469 A1 WO2016134469 A1 WO 2016134469A1 CA 2016050186 W CA2016050186 W CA 2016050186W WO 2016134469 A1 WO2016134469 A1 WO 2016134469A1
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WIPO (PCT)
Prior art keywords
medium
spectrum
emission wavelength
sensor
excitation
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PCT/CA2016/050186
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French (fr)
Inventor
Amir Farzad FORUGHI
Sheldon I. Green
Boris Stoeber
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Astenjohnson, Inc.
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Publication of WO2016134469A1 publication Critical patent/WO2016134469A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/59—Transmissivity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/86—Investigating moving sheets
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/34—Paper
    • G01N33/346—Paper sheets

Definitions

  • an apparatus for measuring moisture content of a porous medium having first and second surfaces comprising: a) an excitation spectrum having a minimum wavelength of 50 nm; b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c) a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the sub-range after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium.
  • the excitation spectrum can be provided by a laser, or by a combination of an energy source and an excitation filter. Furthermore, the excitation spectrum by be directed towards the medium by use of a dichroic mirror.
  • a further option includes the use of an optical apparatus comprising one or more lenses that is placed adjacent the first surface. The optical apparatus can be used to focus the excitation spectrum onto the medium, collect the emission wavelength spectrum and/or guide the emission wavelength spectrum towards the sensor.
  • an apparatus for measuring moisture content of a porous medium comprising hardwood fibres, the porous medium having first and second surfaces comprising: a) an excitation spectrum having a minimum wavelength of 450 run; b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c)a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the sub-range after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium.
  • the excitation spectrum can have a range of from 460 nm to 500 nm;
  • the fluorescing material can be a thermoplastic polymer sheet that comprises a fluorescing dye selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine- 6G, rhodamine-123, fluorescein and pyranine;
  • the emission wavelength spectrum can have a range of from 575 nm to 635 run.
  • the substituted selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine- 6G, rhodamine-123, fluorescein and pyranine
  • the emission wavelength spectrum can have a range of from 575 nm to 635 run.
  • the substituted selected from a substituted aminonaphthylethenylpyridinium
  • aminonaphthylethenylpyridinium (ANEP) dye can be di-8-ANEPPS.
  • the sensor (35) can be an optical sensor (for example, a camera) or a point sensor (for example, a photo detector).
  • the energy source (30) emits an energy spectrum which can be filtered through an excitation filter (40) to produce an excitation range (45) of energy that is used to excite the fluorescing material (25).
  • the energy source can be selected to produce the excitation range (45) directly without the need of the excitation filter (40).
  • the energy spectrum of the excitation range (45) is chosen such that it excites the fluorescing material (25).
  • the energy spectrum of the excitation range (45) can also be chosen so that it does not directly produce fluorescence in the medium (10).
  • the excitation range (45) is directed through the first surface (15) of the medium (10) by use of a dichroic mirror (50) and optical apparatus (47).
  • the excitation range (45) passes through the second surface (20) and strikes the fluorescing material (25), which produces a primary fluorescence in response. A portion of the primary fluorescence radiation passes into the medium (10) through the second surface (20) and out of the medium (10) through the first surface (15).
  • the emergent fluorescent radiation (55) passes through the optical apparatus (47), the dichroic mirror (50) and an emission filter (60) to produce a sub-range (62) of the fluorescent radiation (55), whose intensity (or amplitude) is recorded by the sensor (35).
  • the apparatus can also function without the use of emission filter (60), such that the sensor measures the intensity of the entire fluorescent radiation (55).
  • the emission filter (60) can be designed so that the sub-range (62) covers a range of wavelengths that are longer than the wavelength spectrum of the excitation range (45).
  • FIG 3 is a schematic diagram of a third embodiment of the apparatus (205) used to measure the transmittance of fluorescent radiation through a medium (10).
  • a laser (210) can be used to excite the fluorescing material (25).
  • the laser (210) provides a specific wavelength of excitation (212), rather than the spectrum of energy provided by the excitation range (45) shown in Figs. 1 and 2.
  • a collecting lens (215) can be used to focus the fluorescent response (220), through an emission filter (60), onto a point sensor (225), such as a photo detector, instead of a camera.
  • the photo detector (225) can comprise, for example, a photodiode.
  • the sensor was an sCMOS (scientific CMOS) camera from LaVision while the filter was a commercially-available Nikon filter cube.
  • the fluorescent radiation that passed back through the paper medium was observed using a microscope.
  • Fig. 4 shows a calibration curve for hardwood paper
  • Figs. 5A-5D shows the water content of a 4mm x 4.5mm piece of paper as the paper absorbs water from the top end while all other sides are sealed.
  • the moisture content for the different measurement points has been determined by adding a known amount of water to dry paper in a small closed cavity.
  • the units of intensity are from the camera in the sensor and are digital counts.
  • a 16- bit camera was used for the measurement which provided a linear relationship between the count and the light intensity on the image sensor (W/m ). These counts were normalized by dividing by the count for zero moisture.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

Abstract

An apparatus for measuring electromagnetic radiation transmission through a medium having first and second surfaces, the apparatus comprising: a) an excitation spectrum having a minimum wavelength of 50 nm; b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c) a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; and the sensor measures the intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum after the portion of the fluorescent radiation exits the medium through the first surface.

Description

APPARATUS FOR MEASUREMENT OF OPTICAL TRANSMISSION USING
FLUORESCENCE RADIATION
The present disclosure relates to the measurement of optical transmittance through a medium. In particular, it relates to the transmission of fluorescence radiation through a medium for the purpose of measuring moisture content within the medium.
Conventional transmittance measurement systems measure transmittance through a substance by using both sides of the substance. That is, an energy source passes radiation through one surface of the substance, while a detector measures the transmitted radiation through a second surface.
U.S. Patent No. 3,660,662 discloses a measuring device used to measure the moisture content, the filler content or the content of coating material of a paper web or the like. X-ray fluorescence is used in the method to measure moisture content. Furthermore, the radiation source is on the same side of the paper as the detector, which is located behind the radiation source. A ring-shaped radiation shield is placed between the radiation source and a window of the detector.
The apparatus in its general form will first be described, and then its implementation in terms of embodiments will be detailed hereafter. These embodiments are intended to demonstrate the principles of the apparatus and the manner of implementation. The apparatus in the broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this specification. In one aspect of the present invention, there is provided an apparatus for measuring electromagnetic radiation transmission through a medium having first and second surfaces, the apparatus comprising: a) an excitation spectrum having a minimum wavelength of 50 ran; b)a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c) a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; and the sensor measures the intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum after the portion of the fluorescent radiation exits the medium through the first surface.
In a further aspect of the present invention, there is provided an apparatus for measuring moisture content of a porous medium having first and second surfaces, the apparatus comprising: a) an excitation spectrum having a minimum wavelength of 50 nm; b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c) a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the sub-range after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium.
The minimum wavelength of the excitation spectrum can also be 100 nm. With respect to the medium, it can fluoresce outside the excitation spectrum. In addition, the sub-range of the emission wavelength spectrum can be outside the excitation spectrum.
The excitation spectrum can be provided by a laser, or by a combination of an energy source and an excitation filter. Furthermore, the excitation spectrum by be directed towards the medium by use of a dichroic mirror. A further option includes the use of an optical apparatus comprising one or more lenses that is placed adjacent the first surface. The optical apparatus can be used to focus the excitation spectrum onto the medium, collect the emission wavelength spectrum and/or guide the emission wavelength spectrum towards the sensor.
Another optional feature includes a translucent layer that is is placed adjacent the first surface to prevent moisture loss of the medium.
The fluorescing material can be, for example, a thermoplastic polymer sheet that comprises a fluorescing dye which may be selected from a substituted
aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine-6G, rhodamine- 123, fluorescein and pyranine. An emission filter can be used to produce the sub-range of the emission wavelength spectrum. Different types of sensors can be used to measure the final intensity. For example, the sensor can be an optical sensor (such as, but not limited to, a camera) or a point sensor (such as, but not limited to, a photodetector). Examples of media include a woven fabric, a nonwoven web and a granular medium. The nonwoven web can be paper, while the granular medium may comprise a multiplicity of grains or seeds.
In yet another aspect of the present invention, there is provided an apparatus for measuring moisture content of a porous medium comprising hardwood fibres, the porous medium having first and second surfaces, the apparatus comprising: a) an excitation spectrum having a minimum wavelength of 450 run; b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c)a sensor for measuring an intensity of the emission wavelength spectrum or a sub-range of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the sub-range after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium. The excitation spectrum can have a range of from 460 nm to 500 nm; the fluorescing material can be a thermoplastic polymer sheet that comprises a fluorescing dye selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine- 6G, rhodamine-123, fluorescein and pyranine; and the emission wavelength spectrum can have a range of from 575 nm to 635 run. In particular, the substituted
aminonaphthylethenylpyridinium (ANEP) dye can be di-8-ANEPPS.
The foregoing summarizes the principal features of the apparatus and some optional aspects thereof. The apparatus may be further understood by the description of the embodiments which follow. Wherever ranges of values are referenced within this specification, sub-ranges therein are intended to be included within the scope of the apparatus unless otherwise indicated. Where characteristics are attributed to one or another variant of the apparatus unless otherwise indicated, such characteristics are intended to apply to all other variants where such characteristics are appropriate or compatible with such other variants. BRIEF DESCRIPTION OF FIGURES
Figure 1 is a schematic diagram of a first embodiment of the apparatus. Figure 2 is a schematic diagram of a second embodiment of the apparatus. Figure 3 is a schematic diagram of a third embodiment of the apparatus. Figure 4 illustrates calibration data for hardwood paper. Figures 5 A-5D illustrates a time sequence of moisture content of a paper medium as the medium absorbs water, as measured with the first embodiment of the apparatus.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a schematic diagram of one embodiment of the apparatus (5) used to measure the transmittance of fluorescent radiation through a medium (10). The medium (10) can be porous and generally has two surfaces (15, 20). Each surface (15, 20) can independently be planar. A fluorescing material (25) is placed adjacent the second surface (20) of the medium (10). An optional layer (12) that is translucent or nearly translucent, (for example, a glass slide) can be placed adjacent the first surface (15) of the medium (10). The layer (12) is used when moisture loss through the first surface (15) of the medium is to be avoided. An energy source (30) and a sensor (35) are located on the same side of the medium (10) (that is, near the first surface (15)). The sensor (35) can be an optical sensor (for example, a camera) or a point sensor (for example, a photo detector). In the embodiment shown in Fig. 1, the energy source (30) emits an energy spectrum which can be filtered through an excitation filter (40) to produce an excitation range (45) of energy that is used to excite the fluorescing material (25). Alternatively, the energy source can be selected to produce the excitation range (45) directly without the need of the excitation filter (40). The energy spectrum of the excitation range (45) is chosen such that it excites the fluorescing material (25). The energy spectrum of the excitation range (45) can also be chosen so that it does not directly produce fluorescence in the medium (10). The excitation range (45) is directed through the first surface (15) of the medium (10) by use of a dichroic mirror (50) and optical apparatus (47).
The optical apparatus (47) can comprise an objective lens and other optical parts (for example, an objective turret). The optical apparatus (47) can be a combination of two or more lenses whose functions can include: focusing the narrow band (45) onto the medium (10); collecting the emitted light from the medium (10); and guiding the collected light to the filtering or measuring system (filter-cube, eyepiece, optical sensor or camera).
The excitation range (45) passes through the second surface (20) and strikes the fluorescing material (25), which produces a primary fluorescence in response. A portion of the primary fluorescence radiation passes into the medium (10) through the second surface (20) and out of the medium (10) through the first surface (15). The emergent fluorescent radiation (55) passes through the optical apparatus (47), the dichroic mirror (50) and an emission filter (60) to produce a sub-range (62) of the fluorescent radiation (55), whose intensity (or amplitude) is recorded by the sensor (35). The apparatus can also function without the use of emission filter (60), such that the sensor measures the intensity of the entire fluorescent radiation (55). In addition, the emission filter (60) can be designed so that the sub-range (62) covers a range of wavelengths that are longer than the wavelength spectrum of the excitation range (45).
The strength of the signal detected by the sensor (35) is a function of the content of the medium (10), and in some applications, will be a function of its moisture content. The apparatus (5) allows for transmittance measurement at a single point, averaged over an area, or with spatial resolution over an area, so as to provide a measure of the moisture content of the medium (10). Figure 2 is a schematic diagram of a second embodiment of the apparatus (105) used to measure the transmittance of fluorescent radiation through a medium (10). The part numbers correspond to those in Figure 1. The embodiment represented in Figure 2 illustrates that the excitation range (45) can enter the medium (10) at an angle that is different from the angle at which the fluorescent radiation (55) exits the medium.
Figure 3 is a schematic diagram of a third embodiment of the apparatus (205) used to measure the transmittance of fluorescent radiation through a medium (10). Here, a laser (210) can be used to excite the fluorescing material (25). The laser (210) provides a specific wavelength of excitation (212), rather than the spectrum of energy provided by the excitation range (45) shown in Figs. 1 and 2. In addition, a collecting lens (215) can be used to focus the fluorescent response (220), through an emission filter (60), onto a point sensor (225), such as a photo detector, instead of a camera. The photo detector (225) can comprise, for example, a photodiode.
The apparatus can be used to measure the moisture content of paper and related cellulosic products, as described below.
Experimental
The present method of measuring of the moisture content of paper was tested using a planar paper web formed from hardwood fibers. A thermoplastic polymer sheet, which included a red dye in the polymer melt, was used as the fluorescing material. The dye was an ANEPPS dye (substituted aminonaphthylethenylpyridinium (ANEP) dyes, in particular di-8- ANEPPS). Other examples of fluorescent materials that can be used, include (but are not limited to) a sheet coated by, or comprising, Rhodamine-B, Rhodamine-6G, Rhodamine-123, Fluorescein or Pyranine.
It should be noted that some mediums are auto-fluorescent for some excitation wavelengths. For example, paper is auto-fluorescent for ultraviolet (UV) and green wavelengths of incident radiation. In this application (i.e. the measurement of moisture content of paper), the excitation wavelengths were therefore selected outside these ranges to minimize interference between the fluorescent response of the medium (paper), and the response from the fluorescent material (the polymer sheet). When measuring the moisture content of paper, the incident excitation spectrum can have a blue wavelength, in order to avoid interference from any fluorescence response of the paper. There are different materials that can be excited by incident blue light and produce a fluorescence response that is red; one example is the series of ANEPPS dyes.
The fluorescing response of the polymer sheet can lead to a secondary fluorescence response in the medium (paper). However, due to Stokes law, the wavelength of the fluorescence response is always longer than the excitation wavelength. Therefore, by using an appropriate emission filter, secondary fluorescence response is not measured by the sensor.
It has been found that how the transmittance of paper (in the visible spectrum) varies with its moisture content, is almost independent of the particular transmission wavelength. Therefore, there is no preferred wavelength for the moisture measurement. In an embodiment of the apparatus, a planar sheet of a paper medium (comprising hardwood fibers) was exposed to an excitation range of between 460-5 OOnm. The light source used to generate the excitation range was a mercury arc lamp that was filtered by a standard commercial band pass filter. A portion of the light passed through the paper medium and reached the fluorescent material, which then emitted light at a second wavelength range of 575-635nm. The fluorescent radiation passed through a Di-8-ANEPPS filter before reaching a sensor. The sensor was an sCMOS (scientific CMOS) camera from LaVision while the filter was a commercially-available Nikon filter cube. The fluorescent radiation that passed back through the paper medium was observed using a microscope. Fig. 4 shows a calibration curve for hardwood paper, while Figs. 5A-5D shows the water content of a 4mm x 4.5mm piece of paper as the paper absorbs water from the top end while all other sides are sealed.
In Fig. 4, the moisture content for the different measurement points (dots) has been determined by adding a known amount of water to dry paper in a small closed cavity. In this figure, the units of intensity are from the camera in the sensor and are digital counts. A 16- bit camera was used for the measurement which provided a linear relationship between the count and the light intensity on the image sensor (W/m ). These counts were normalized by dividing by the count for zero moisture.
Figures 5A-5D are time-lapsed images of a small cross-section of a sheet of paper as it absorbs water from the top side of the image. The moisture content of the paper medium is measured with the embodiment of the apparatus described in Fig. 1. The bottom end of the imaged medium is near zero humidity while the top end contains up to 1.2 times the mass of water compared to the mass of paper. The time between successive images 5A to 5D is approximately 1 second. The gray-scale on the right hand side labeled "Moisture content (%)" is the legend for the associated photograph on the left. The gray-scale indicates the moisture content of the paper. Thus, for example, if the paper locally has a dry weight of 50 grams per square meter, and the wet weight is 110 grams per square meter, the local moisture content is (110-50)/50=120%. The units along the lower horizontal edge and the left vertical edge are in microns.
The foregoing has constituted a description of specific embodiments showing how the apparatus may be applied and put into use. These embodiments are only exemplary. The apparatus in its broadest and more specific aspects are further described and defined in the claims which now follow.

Claims

CLAIMS:
1. An apparatus for measuring electromagnetic radiation transmission through a medium having first and second surfaces, the apparatus comprising:
a) an excitation spectrum having a minimum wavelength of 50 nm;
b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and c) a sensor for measuring an intensity of the emission wavelength spectrum or a subrange of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; and the sensor measures the intensity of the emission wavelength spectrum or a subrange of the emission wavelength spectrum after the portion of the fluorescent radiation exits the medium through the first surface.
2. The apparatus of claim 1, wherein the minimum wavelength is 100 nm.
3. The apparatus of claim 1 or 2, wherein the medium fluoresces outside the excitation spectrum.
4. The apparatus of any one of claims 1 to 3, wherein the sub-range is outside the excitation spectrum.
5. The apparatus of any one of claims 1 to 4, wherein a laser provides the excitation
spectrum.
6. The apparatus of any one of claims 1 to 4 wherein an energy source and an excitation filter are combined to provide the excitation spectrum.
7. The apparatus of any one of claims 1 to 6, wherein a dichroic mirror directs the excitation spectrum towards the medium.
8. The apparatus of any one of claims 1 to 7, wherein an optical apparatus comprising one or more lenses, is placed adjacent the first surface, the optical apparatus used for at least one of: focusing the excitation spectrum onto the medium; collecting the emission wavelength spectrum; and guiding the emission wavelength spectrum towards the sensor.
9. The apparatus of any one of claims 1 to 8, wherein a translucent layer is placed adjacent the first surface to prevent moisture loss of the medium.
10. The apparatus of any one of claims 1 to 9, wherein the fluorescing material is a
thermoplastic polymer sheet that comprises a fluorescing dye.
11. The apparatus of claim 10, wherein the fluorescing dye is selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine-6G, rhodamine- 123, fluorescein and pyranine.
12. The apparatus of any one of claims 1 to 11, wherein the sub-range is produced by an emission filter.
13. The apparatus of any one of claims 1 to 12, wherein the sensor is an optical sensor.
14. The apparatus of any one of claims 1 to 12, wherein the sensor is a point sensor.
15. The apparatus of any one of claims 1 to 14, wherein the medium is a woven fabric, a nonwoven web or a granular medium.
16. An apparatus for measuring moisture content of a porous medium having first and second surfaces, the apparatus comprising:
a) an excitation spectrum having a minimum wavelength of 50 nm;
b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and
c) a sensor for measuring an intensity of the emission wavelength spectrum or a subrange of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the subrange after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium.
17. The apparatus of claim 16, wherein the minimum wavelength is 100 nm.
18. The apparatus of claim 16 or 17, wherein the medium fluoresces outside the excitation spectrum.
19. The apparatus of any one of claims 16 to 18, wherein the sub-range is outside the
excitation spectrum.
20. The apparatus of any one of claims 16 to 19, wherein a laser provides the excitation
spectrum.
21. The apparatus of any one of claims 16 to 20 wherein an energy source and an excitation filter are combined to provide the excitation spectrum.
22. The apparatus of any one of claims 16 to 29, wherein a dichroic mirror directs the excitation spectrum towards the medium.
23. The apparatus of any one of claims 16 to 22, wherein an optical apparatus comprising one or more lenses, is placed adjacent the first surface, the optical apparatus used for at least one of: focusing the excitation spectrum onto the medium; collecting the emission wavelength spectrum; and guiding the emission wavelength spectrum towards the sensor.
24. The apparatus of any one of claims 16 to 23, wherein a translucent layer is placed
adjacent the first surface to prevent moisture loss of the medium.
25. The apparatus of any one of claims 16 to 24, wherein the fluorescing material is a
thermoplastic polymer sheet that comprises a fluorescing dye.
26. The apparatus of claim 25, wherein the fluorescing dye is selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine-6G, rhodamine- 123, fluorescein and pyranine.
27. The apparatus of any one of claims 16 to 26, wherein the sub-range is produced by an emission filter.
28. The apparatus of any one of claims 16 to 27, wherein the sensor is an optical sensor.
29. The apparatus of any one of claims 16 to 27, wherein the sensor is a point sensor.
30. The apparatus of any one of claims 16 to 29, wherein the porous medium is a woven fabric, a nonwoven web or a granular medium.
31. The apparatus of claim 30, wherein the nonwoven web is paper.
32. The apparatus of claim 30, wherein the granular medium comprises a multiplicity of grains or seeds.
33. The apparatus of claim 32, wherein the granular medium is a multiplicity of grains or seeds.
34. An apparatus for measuring moisture content of a porous medium comprising hardwood fibres, the porous medium having first and second surfaces, the apparatus comprising: a) an excitation spectrum having a minimum wavelength of 450 ran;
b) a fluorescing material that fluoresces within the excitation spectrum and emits fluorescent radiation within an emission wavelength spectrum; and
c) a sensor for measuring an intensity of the emission wavelength spectrum or a subrange of the emission wavelength spectrum; wherein: the fluorescing material is placed adjacent the second surface; the excitation spectrum enters the medium through the first surface, exits through the second surface, and strikes the fluorescing material; a portion of the fluorescent radiation enters the medium through the second surface and exits the medium through the first surface; the sensor measures the intensity of the emission wavelength spectrum or the subrange after the portion of the fluorescent radiation exits the medium through the first surface; and the intensity of the emission wavelength spectrum or the sub-range, is compared to calibration data or theoretical data of the moisture content of the porous medium.
35. The apparatus of claim 5, wherein the excitation spectrum has a range of from 460 nm to 500 nm; the fluorescing material is a thermoplastic polymer sheet that comprises a fluorescing dye selected from a substituted aminonaphthylethenylpyridinium (ANEP) dye, rhodamine-B, rhodamine-6G, rhodamine-123, fluorescein and pyranine; and the emission wavelength spectrum has a range of from 575 nm to 635 nm.
36. The apparatus of claim 35, wherein the substituted aminonaphthylethenylpyridinium
(ANEP) dye is di-8-ANEPPS.
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US20090237501A1 (en) * 2008-03-19 2009-09-24 Ruprecht-Karis-Universitat Heidelberg Kirchhoff-Institut Fur Physik method and an apparatus for localization of single dye molecules in the fluorescent microscopy

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